2013-08-012024-05-13https://scholars.lib.ntu.edu.tw/handle/123456789/643950摘要：砷 (arsenic)廣泛分佈於地球環境，包括無機砷和有機砷，無機砷被認為較有機砷具有毒性，並且為人類的主要暴露來源。砷可分佈於生物體的毛髮，牙齒，內臟，指甲及骨骼等。有研究指出在美國和其他國家長期暴露於含砷之飲用水，會提高多種慢性疾病之發生率如癌症、周邊血管疾病、內分泌功能失調、糖尿病等。砷會累積在骨骼及骨髓中，骨組織被認為也是砷的目標器官之一。砷具有引起骨髓細胞毒性的能力；急性或慢性砷中毒已知會造成骨髓抑制，影響造血功能。有關砷對於骨骼系統的毒性及機制研究相對地少很多。負責骨生成的造骨細胞來自於骨髓中的間質幹細胞分化而成，而負責骨吸收的破骨細胞則來自造血幹細胞。當調控骨質之因子失調後會造成骨生成和骨吸收失去平衡進而產生骨質疏鬆症；但當間質幹細胞趨向於分化成脂肪細胞也會影響骨質疏鬆症發生。最近研究指出三價無機砷會引起骨髓間質幹細胞毒性；而三氧化二砷也會造成人類造骨細胞凋亡。但這些研究所使用的砷濃度屬於具細胞毒性之較高劑量範圍。目前尚無砷會影響正常骨髓幹細胞分化的有關報告，尤其是在不具細胞毒性之劑量範圍；而且也缺乏砷與骨質疏鬆症關係之文獻。近年來許多研究致力於骨質疏鬆症之病因及病理機制探討，其中包括糖尿病、內分泌系統及環境污染物等。故有關砷與骨質疏鬆症的關聯之研究有其重要性，值得深入探討。本計畫的目的在於利用細胞及實驗動物模式探討砷在不具細胞毒性之低劑量範圍內，對於骨髓幹細胞分化的影響及可能作用機制，以進一步對於砷在骨質疏鬆症上之可能角色的評估。我們的第一年計畫部分研究成果(收載2011/08/01-2011/12/15期間數據)顯示砷化合物在不造成細胞死亡的劑量下會抑制骨髓幹細胞對於造骨細胞的分化，其會透過減少osteocalcin 和bone morphogenetic protein-2的表現造成骨生成的抑制作用，而細胞訊息蛋白ERK磷酸化的促進可能扮演重要角色。而砷化合物在不造成細胞死亡的劑量下會促進骨髓幹細胞對於脂肪細胞的分化，其中促進細胞訊息蛋白PPARγ的表現可能扮演重要角色。第一年計畫部分研究成果提供了本研究可行性及進一步動物實驗模式探討的基礎；因此，我們計畫繼續完成後面兩年之動物實驗部分，以完整達成本研究計畫之目的及目標。後面兩年之動物實驗部分：第一年(原第二年)：實驗動物及合併一型糖尿病實驗動物模式：選擇低劑量範圍(0.01-2.5 ppm)的砷化合物，探討實驗動物或合併骨質疏鬆症危險因子-一型糖尿病長期飲水砷暴露，是否會影響骨髓幹細胞分化，並誘導或加重骨質疏鬆症的發生，及其可能之細胞機制；第二年(原第三年)：實驗動物及合併雌激素缺乏實驗動物模式：選擇低劑量範圍(0.01-2.5 ppm)的砷化合物，探討實驗動物或合併骨質疏鬆症危險因子-雌激素缺乏狀態(切除卵巢)長期飲水砷暴露，是否會影響骨髓幹細胞分化，並誘導或加重骨質疏鬆症的發生，及其可能之細胞機制。本研究結果將可讓我們進一步了解低劑量範圍的砷化合物是否會影響骨髓幹細胞之生長/功能/分化和可能的分子機制，以及提供基礎醫學研究證據，來說明砷在骨質疏鬆症上之可能角色。<br> Abstract: Arsenic is widely distributed in the Earth's environment as a toxic metalloid element. Inorganic arsenic is considered toxic than organic arsenic, and is the main human exposure source. Long-term exposure to arsenic in drinking water has been shown to increase the incidence of several chronic diseases in the United States and other countries. Bone tissue is considered one of the target organ of arsenic. Arsenic has the ability to cause bone marrow toxicity. Arsenic are known to accumulate in bone and bone marrow; but in comparison to other systems, the researches for arsenic toxicity and its related mechanisms in skeletal system are small lot. Bone formation is caused by osteoblasts derived from bone marrow mesenchymal stem cells (MSCs), and osteoclasts derived from hematopoietic stem cells (HSCs) lead to bone resorption. The dysfunction of regulating factors will result in the loss of balance of bone formation and bone resorption, and thus cause osteoporosis. Recent studies have shown that the trivalent inorganic arsenic can cause toxicity of MSCs, and arsenic trioxide also causes apoptosis in human osteoblasts. However, the concentrations of arsenic used in these studies are of high cytotoxic dose ranges. There are no scientific reports on the effects of arsenic on the differentiation in normal bone marrow stem cells, especially in the non-cytotoxic dose ranges; the literatures for the relationship between arsenic and osteoporosis are also few. In recent years, many studies dedicated to the causes of osteoporosis and its pathological mechanisms. Thus, the study of arsenic associated with osteoporosis is of importance, worthy of further exploration. The aims of this project are to use the cell and experimental animal models to explore the effects of non-cytotoxic low-dose arsenic on the differentiation of bone marrow stem cells and its possible mechanisms, and to further evaluate the possible roles of arsenic in osteoporosis. First-year project, which is being implemented, uses cell models to investigate the actions and molecular mechanisms of non-cytotoxic low-dose arsenic. The part of results of the first year research project (data collection during 2011/08/01-2011/12/15) showed that non-cytotoxic doses of arsenic possess the ability to inhibit the osteoblast differentiation from MSCs via the inhibition of osteocalcin and bone morphogenetic protein-2. The enhancement of ERK phosphorylation by arsenic may play an important role in arsenic-induced osteoblastogenesis inhibition. Moreover, low-dose arsenic could increase the adipogenesis, which may be through a PPARγ-related signaling pathway. These results supply the basis to perform the animal experiments in second and third years. First year (original second year): experimental animals with or without type 1 diabetes: Choose low-dose range (0.01-2.5 ppm) of inorganic arsenic to investigate their long-term effects on bone marrow stem cell differentiation and the incidence of osteoporosis and the possible cellular mechanisms in experimental animals with or without type 1 diabetes exposed to arsenic in drinking water. Second year (original third year): experimental animals with or without estrogen deficiency: Choose low-dose range (0.01-2.5 ppm) of inorganic arsenic to investigate their long-term effects on bone marrow stem cell differentiation and the incidence of osteoporosis and the possible cellular mechanisms in experimental animals with or without estrogen deficiency (ovariectomy) exposed to arsenic in drinking water. The results of this study will help us understand low-dose arsenic compounds affecting bone marrow stem cell growth/function/differentiation and its possible molecular mechanisms, and provide the evidence of basic medical research on the possible role of arsenic in osteoporosis.砷骨髓幹細胞骨質疏鬆症ArsenicBone marrow stem cellsOsteoporosis